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https://issues.apache.org/jira/browse/MAPREDUCE-4868?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jerry Chen updated MAPREDUCE-4868:
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Description:
Currently, the Mapper class allows advanced users to override "public void
run(Context context)" method for more control over the execution of the mapper,
while Context interface limit the operations over the data which is the
foundation of "more control".
One of use cases is that when I am considering a hive optimziation problem, I
want to go two passes over the input data instead of using a another job or
task ( which may slower the whole process). Each pass do the same thing but
with a different parameters.
This is a new paradigm of Map Reduce usage and can be archived easily by extend
Context interface a little with the more control over the data such as reset
the input.
was:
Currently, the Mapper class allows advanced users to override "public void
run(Context context)" method for more control over the map the execution of the
mapper, while Context interface limit the operations over the data which is the
foundation of "more control".
One of use cases is that when I am considering a hive optimziation problem, I
want to go two passes over the input data instead of using a another job or
task ( which may slower the whole process). Each pass do the same thing but
with a different parameters.
This is a new paradigm of Map Reduce usage and can be archived easily by extend
Context interface a little with the more control over the data such as reset
the input.
> Allow multiple iteration for map
> --------------------------------
>
> Key: MAPREDUCE-4868
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4868
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: mrv2
> Affects Versions: 3.0.0, 2.0.3-alpha
> Reporter: Jerry Chen
> Fix For: 3.0.0, 2.0.3-alpha
>
> Original Estimate: 168h
> Remaining Estimate: 168h
>
> Currently, the Mapper class allows advanced users to override "public void
> run(Context context)" method for more control over the execution of the
> mapper, while Context interface limit the operations over the data which is
> the foundation of "more control".
> One of use cases is that when I am considering a hive optimziation problem, I
> want to go two passes over the input data instead of using a another job or
> task ( which may slower the whole process). Each pass do the same thing but
> with a different parameters.
> This is a new paradigm of Map Reduce usage and can be archived easily by
> extend Context interface a little with the more control over the data such as
> reset the input.
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